As a method of forming a fine structure in a manufacturing process of a semiconductor, a nanoimprint lithography (NIL) is used. The NIL is a technology of transferring a pattern onto resist by bringing a unit-magnification template (hereinafter, template) on which a fine pattern that is the same size as a feature size is formed by an electron beam (EB) exposure or the like into contact with a process target substrate to which the resist is applied.
In such pattern formation by the NIL, resist remains in a recess portion (corresponding to a projection portion of the template) of a resist pattern on the process target substrate. The film thickness of this residual portion of the resist is typically called Residual Layer Thickness (RLT), which is an evaluation index of process stability in the NIL.
After the NIL, a pattern is formed on the process target substrate by etching the process target substrate with the resist pattern formed by the NIL as a mask. As above, because resist remains also in the recess portion of the resist pattern, an etching condition needs to be determined by taking it also into account. In other words, even if the dimension of the resist pattern is finished uniformly, the pattern dimension of the processed process target substrate may vary due to variation in RLT.
Moreover, in the NIL, a pattern formed on the template is transferred onto resist in the same size. Therefore, accuracy in pattern in the template greatly affects variation in final feature size of the process target substrate. Illumination unevenness and effect of aberration also affect the dimension variation in a shot in a normal photolithography in addition to an error in a photomask dimension. However, in the NIL, it can be said that most of the dimension variation in a shot is due to the dimension variation of the template.
On the other hand, a manufacturing accuracy is extremely severe in the template for the NIL compared to a quadruple photomask used in the normal photolithography. Typically, the photomask and the template are manufactured by using an electron beam lithography. For example, when a line and space (L/S) of 50 nm pitch is needed on a wafer, an L/S pattern of 200 nm pitch is manufactured on the quadruple photomask. However, on the template for the NIL, an L/S pattern of 50 nm pitch that is the same as an actual feature size is manufactured. Therefore, the manufacturing accuracy is severe in the unit-magnification template for the NIL compared to the quadruple photomask, so that variation in pattern dimension easily occurs.
As a technology to address a problem attributed to the dimension variation of the template, for example, Japanese Patent Application Laid-open No. 2007-296783 proposes a method of applying resist so that the distance between a mold and a substrate in a pressing process becomes uniform in accordance with the shape and the thickness distribution of the mold (template) and the process target substrate. With this method, it is possible to shorten the time required for the pressing process by preventing increase in pressing time attributed to flatness such as thickness, undulation, or the like of the mold and the process target substrate, so that throughput can be improved.